Functionalized thermoplastic elastomer

ABSTRACT

A thermoplastic elastomer produced without a hydrogenation step is functionalized utilizing a free radical initiator and a functionalizing monomer having at least one point of unsaturation. The base polymers can be produced by copolymerizing an α-olefin capable of producing an amorphous backbone with a comonomer which provides a “hook” for grafting to with a living polystyrene chain. Another method is to copolymerize an α-olefin monomer system capable of producing an amorphous backbone with a comonomer containing a functional group from which an anionically polymerizable monomer is grown from the backbone. A third method involves copolymerizing an α-olefin monomer system capable of giving an amorphous backbone with an olefin-terminated polystyrene comonomer. In a less preferred embodiment, a conventional EPDM polymer can be metallated and a monoalkenyl aromatic compound anionically polymerizable monomer grown from the backbone.

BACKGROUND OF THE INVENTION

[0001] This invention relates to functionalized polymers.

[0002] Synthetic polymers are generally characterized as either resinousor elastomeric. Historically, elastomeric polymers required chemicalvulcanization before they possessed sufficient strength for utilitiessuch as tire treads, shoe soles, rubber bands, and other elasticutilities requiring some level of strength. However, these compositionsafter vulcanization were no longer thermoplastic.

[0003] In the 1960s a major advance in the art occurred with thediscovery and commercialization of thermoplastic elastomers. Thesematerials possess an internal elastomeric block and a plurality ofterminal aromatic blocks. On cooling from a melt, such compositionsexhibit high tensile strength, high elongation, and rapid and almostcomplete recovery after elongation. This is attributed to the fact thatin the bulk state, the aromatic end segments of these block copolymersagglomerate. At temperatures significantly below the glass transitiontemperature (T_(g)) of the aromatic end blocks, these agglomerations(domains) act as strong, multifunctional junction points and so thecopolymers behave as though they are joined in a cross-linked network.

[0004] Such polymers are non-polar and hence are sometimes not ideallysuited for applications that require adhesion to polar substrates orthat require compatibility with polar polymeric materials. This can beovercome by incorporating a functional group on the polymer. However,these polymers contain a large amount of aliphatic unsaturation in thediene blocks which can result in cross-linking and gellation of polymerchains during the free-radical grafting reactions used to incorporatepolar functional groups. Hence, it is necessary to utilize ahydrogenation step prior to incorporating a functional group.Hydrogenation can be accomplished using any of several hydrogenationprocesses known in the art. For instance, the commonly used method is toemploy a Group VIII metal catalyst, particularly nickel or cobalt, witha suitable reducing agent such as an aluminum alkyl to catalyze thehydrogenation. The disadvantage in this is the necessity for theadditional hydrogenation and catalyst removal steps. These steps areequipment and time intensive and thereby increase the complexity andcost of producing functionalized thermoplastic-plastic elastomers. Inaddition, the hydrogenation catalysts are sensitive to certain poisons,making hydrogenation of polymers containing particular functional groupsor coupling agent residues difficult or impossible.

[0005] Thus, it would be highly desirable to have a process by whichfunctionalized thermoplastic elastomers could be directly producedwithout the necessity of a hydrogenation step.

SUMMARY OF THE INVENTION

[0006] It is an object of this invention to provide functionalizedthermo-plastic elastomers without the utilization of a hydrogenationstep.

[0007] In accordance with this invention a thermoplastic elastomer isprepared with an amorphous olefin or EPDM backbone and a plurality ofpendant aromatic side chains and thereafter contacted with a reactivefunctional monomer in the presence of a free radical initiator.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Surprisingly, it has been found that even though α-olefinamorphous backbones inherently contain a regular pattern of alkyl sidechains which are a potential source of Beta-scission, thermoplasticelastomers having such backbones can be functionalized and still retaina significant amount of strength.

[0009] Amorphous Backbone

[0010] There are two embodiments to this invention. In the first andpreferred embodiment there is an all α-olefin amorphous backbone. Inthis embodiment the backbone is made of an olefin monomer or a mixtureof olefin monomers and a comonomer. The monomer is either a C₄ to C₃₀α-olefin (or mixtures thereof) or ethylene and a higher α-olefin secondmonomer (higher than ethylene, i.e. C₃ and higher). As a practicalmatter, the second monomer will almost always be a C₃ to C₅ α-olefinsince there would be little point in utilizing a C₆ or higher secondmonomer since an amorphous backbone can be made directly from a C₆α-olefin, if desired. Broadly, however, the second monomer can be any C₃to C₃₀ α-olefin. The preferred monomers are hexene, octene,ethylene/propylene and ethylene/butene. When the backbone is made from acombination of ethylene and a C₃ or higher α-olefin, the C₃ or higherα-olefin is used in a mole ratio of 20 to 40, preferably 30 to 40, morepreferably 30 to 35 percent.

[0011] There are three aspects to this first embodiment of theinvention. In the first aspect, the comonomer is a 1-alkenyl compoundcontaining a functional group to which an anionic polymer can be grafted“to” to produce a pendant graft block side chain.

[0012] Suitable comonomers are those having the formula

CH₂═CH—(CH₂)_(n)—Y

[0013] where n≧0 and Y is selected from the group including halosilanegroups, hydridosilane groups, ester groups, aldehyde groups, ketones,halogens, epoxides, and phosphorous groups of the formula P-Z₂ where Zis Cl, Br, I, F, hydrogen, ester groups, or combinations of these.

[0014] The preferred 1-alkenylhalosilane compounds which can be used inthe present invention include H₂C═CH—(CH₂)_(n)—SiX₃ where n≧0;X=halogen, R or H or combinations thereof, R is alkyl, or aryl; and atleast one X must be halogen. This definition of R is in the context of a1-alkenylhalosilane, R being used in other contexts hereinafter.Similarly X is used in another context later. H₂C═CH—(CH₂)_(n)—SiMe₂Clis preferred because when the presence of ungrafted anionic polymer inthe final product is undesirable, this halosilane may easily be removedfrom the backbone copolymer due to its high volatility.

[0015] Also preferred for the same reason are hydrosilane compounds ofthe formula

CH₂═CH—(CH₂)_(n)SiH_(x)R_(y)

[0016] where n≧0, x+y=3, x≧1, and y≦2. Most preferred compounds havethese structures: CH₂═CH—CH₂—SiH₃, CH₂═CH—SiH₃, CH₂═CH—SiH₂CH₃, andCH₂═CH—CH₂—SiR₂CH₃. In the last two structures halogen may take theplace of H, in which case the silanes would be halosilanes.

[0017] In the second aspect of this first embodiment, the comonomer is avinyl aromatic compound represented by the general formula

[0018] wherein n is an integer of 0 to 20, or an alkenyl alkyl or arylsilane represented by the formula:

CH₂═CH—(CH₂)_(n)—SiR_(m)H_(x)  (2)

[0019] where n is 0 or an integer of from 1 to 12; R is alkyl or aryl,preferably methyl, phenyl, or ethyl; x is 0 or 1; m is 2 or 3; and x+m3. The most preferred alkenyl silanes for use herein areallyltrimethylsilane and allyl dimethylsilane because they are mostreactive to copolymerization with α-olefins. This forms a copolymerwhich becomes the backbone of the graft block copolymer of the presentinvention.

[0020] In this aspect of the first embodiment, the comonomer contains afunctional group. In the case of the first formula, the benzylic carbonatom imparted by the comonomer can be deprotonated by a metallatingagent such as RLi and the resulting structure behaves in a mannersimilar to styrene anions. Thus, while the vinyl aromatic comonomermight not normally be thought of as imparting a functional group onincorporation into the polymer chain, the benzylic hydrogen isfunctional to the metallating agent. In the case of the second formula,the R group can be deprotonated by the metallating agent. From thismetallated functional group a monovinyl arene anionically polymerizablemonomer is grown “from” the backbone to form pendant aromatic sidechains.

[0021] In the third aspect of this first embodiment of the invention,the comonomer is an olefin capped aromatic polymer chain utilized togive aromatic side chains of sufficient length and number to formresinous or glassy domains. The comonomer is produced by anionicpolymerization of a monoalkenyl aromatic compound having 8 to 20 carbonatoms with alkenyl groups of up to 3 carbon atoms attached to a benzenering as exemplified by styrene and styrene homologs such asethylvinylbenzene, α-methylstyrene and paramethylstyrene. Styrene andα-methylstyrene are particularly preferred monoalkenyl aromaticcompounds, especially styrene.

[0022] The initiator systems used in the first step of producing thesemacromonomers are those conventionally used in the art. They generallyare those of the general formula RLi where R is a hydrocarbyl radical of1 to about 20 carbon atoms. This is the definition of R in the contextof RLi, R being used later in a different context. Examples of suchlithium initiators are methyllithium, isopropyllithium, n-butyllithium,sec-butyllithium, t-butyllithium, n-dodecyllithium, cyclohexyllithium,and 4-cyclohexyllithium. Preferred are n-butyllithium andsec-butyllithium. The amount of the lithium metal initiator employeddepends upon the desired molecular weight of the macromonomer. Normally,the organomonollithium initiator is employed in the range of about 0.1to 200, preferably 2 to 30 millimoles per 100 grams of total monoalkenylaromatic monomer.

[0023] The polymerization reaction to produce the comonomer (macromer)precursor can be carried out in the presence of a hydrocarbon diluent.Preferably the hydrocarbon diluent is a paraffinic, cyclo-paraffinic oraromatic hydrocarbon having 4-10 carbon atoms or a mixture of suchdiluents. Examples for the diluent are n-hexane, n-heptane,2,2,4-trimethylpentane, cyclohexane, benzene and toluene. Cyclohexane isgenerally the preferred paraffinic solvent.

[0024] It is preferred, however, to carry out the initiation of thearomatic macromonomer precursor in the presence of an α-olefin diluentand thereafter to end cap the resulting alkali metal terminated livingpolymer chain in the presence of the same diluent.

[0025] The reaction is generally carried out with a weight ratio ofdiluent to monomers exceeding 1. Preferably the diluent is employed in aquantity between about 2 to about 20 parts by weight, most perfably 3 to10 parts by weight, per 1 part by weight of total anionicallypolymerizable monomers. The term “anionically polymerizable monomer”refers to the monomer utilized to prepare the comonomer precursor.

[0026] The polymerization to produce the macromer precursor usuallyoccurs within a period of time ranging from 1 minute up to about 6hours. Preferably, the reaction is carried out within a time period ofabout 10 minutes to about 2 hours. The polymerization temperature is notcritical and will generally be in a range of from about 15° to about150° C., preferably in a range of about 40° to about 90° C. If thepolymerization is carried out at a temperature above the boiling pointof the reaction mixture, then reflux and/or elevated pressure can beused to maintain liquid conditions in the reaction medium.

[0027] Various materials are known to be detrimental to the lithiummetal-initiated polymerization. Particularly, the presence of carbondioxide, oxygen, water and alcohols should be avoided during theorganollithium-initiated polymerization reaction to produce the alkalimetal terminated macromer precursor.

[0028] It is also within the scope of this invention to use anunsaturated initiator such as vinyl lithium or allyl lithium. After thepolymerization the lithium end can simply be terminated in aconventional manner, i.e. with an alcohol, and the vinyl at the otherend provides the polymerizable entity; or the lithium can be reactedwith an olefinic halosilane to give an α,ω-olefin if some crosslinkingwere desired.

[0029] Subsequent to the above-described initiation of the macromerprecursor, the resulting living aromatic polymer chain is capped to givea terminal α-olefin. This is done with an alkenyl halosilane having onlyone halogen atom as represented by the following general formula

[0030] wherein n is an integer of from 0 to 16, preferably 0 to 6, R isan alkyl generally having 1 to 10 carbon atoms and preferably methyl andX is a halogen, preferably chlorine. Thereafter, the resultingα-olefin-terminated aromatic macromonomeric comonomer (macromer) isreacted with the α-olefin monomer (or monomers) described previously.

[0031] One embodiment of this invention is exemplified as follows

[0032] In this preferred embodiment, the alkyl alkali metal initiator isreacted with the monoalkenyl aromatic compound to give the livingaromatic polymer chain in the olefin solvent. This is the comonomerprecursor. Thereafter, this living aromatic polymer chain is reactedwith the alkenyl halosilane to give the macromer comonomer, also in thepresence of olefin solvent. Finally, the comonomer is copolymerized withα-olefin monomer in a solventless system (the only diluent beingα-olefin monomer). Most preferably, the diluent all through thisoperation is the same α-olefin as that used as the monomer in the finalcopolymerization reaction. However, any α-olefin monomer capable ofbeing liquid under the pressure and temperature conditions beingemployed can be used as the diluent. Preferred are C₄-C₁₂ α-olefins,most preferably hexene, octene and decene.

[0033] Broadly then, the comonomer is represented by the general formula

[0034] where R′ is the remnant of the organollithium initiator, R″ is apolymerized arene unit, R is alkyl as noted above, x is an integersufficient that the comonomer exhibits a molecular weight within therange of 500-30,000, preferably 1000-21,000, most preferably 5000-20,000and n is an integer of from 0 to 16, preferably 0 to 6. Thus, oncopolymerization the side chains are represented by the general formula

[0035] The comonomer is employed in an amount sufficient to giveincorporation of about 5 to 49 weight percent comonomer based on thetotal weight of incorporated monomer and comonomer. Preferably, theincorporated weight of comonomer is within the range of 10 to 40, morepreferably 15 to 35 weight percent based on the total weight of thecopolymer. The weight percent glassy regions of the final polymer willclosely approximate the weight percent comonomer since the backbone isessentially amorphous and the polymerized comonomer chainspre-dominantly form glassy domains.

[0036] While the individual aromatic side chains are generally lowermolecular weight than the end blocks of prior art thermoplasticelastomers, they still form glassy domains to “crosslink” the polymer togive strength while the amorphous backbone imparts elastomericcharacteristics.

[0037] Thus, in this aspect of the first embodiment the thermoplasticelastomer to be functionalized is already complete whereas in the firsttwo aspects of the first embodiment, the side chains remain to beprovided.

[0038] Methods for carrying out the copolymerization of the α-olefinbackbone monomer and the comonomer for all three aspects of the firstembodiment of this invention include the use of metallocene orZiegler-Natta catalysis as well as cationic polymerization. Othermethods include free radical or Lewis acid catalyzed processes.

[0039] Metallocene catalysts are organometallic coordination compoundsobtained as a cyclopentadienyl derivative of a transition metal or metalhalide. Their use in the polymerization of olefins is well known.

[0040] A useful Ziegler-Natta catalysis process is described in Asanuma,U.S. Pat. No. 5,045,597 (Sep. 3, 1991) which is herein incorporated byreference. The Ziegler-Natta method of polymerization requires thepresence of a catalyst which includes a transition metal compound andwhich also utilizes an aluminum compound as well as an electron donor.Such transition metal compounds include titanium halides such astitanium tetrachloride, magnesium alkoxide supported titaniumtetrachloride and certain metallocenes of zirconium, titanium, andhafnium which are known from the art to polymerize α-olefins. Thealuminum compound is usually an organo aluminum compound which ispreferably selected from the group consisting of trialkyl aluminum,dialkylaluminum halides, alkyl aluminum sesquihalides, alkyl aluminumdihalides and aluminoxanes. There are a wide variety of electron donorswhich can be used and they are usually oxygen or nitrogen containingcompounds such as ethers, esters, ortho ethers, alkoxy-siliconcompounds, and heterocyclic aromatic nitrogen compounds.

[0041] The Ziegler-Natta polymerization may be conducted in neatmonomer, by solvent polymerization, or by vapor phase polymerization.Generally, the polymerization is conducted at a temperature of from 30°C. to 100° C. under a pressure of from atmospheric to the vapor pressureof the 1-alkenyl functionalized monomer at the polymerizationtemperature and optionally in the presence of a molecular weight controlagent such as hydrogen.

[0042] Thermoplastic elastomers require an amorphous polymer backboneand glassy or semicrystalline polymer grafts. Other catalysts suitablefor producing amorphous polymer backbones are described in Job, U.S.Pat. No. 5,122,494 (Jun. 16, 1992), Job, U.S. Pat. No. 5,089,573 (Feb.18, 1992), Job et al, U.S. Pat. No. 5,118,768 (Jun. 2, 1992), Job, U.S.Pat. No. 4,874,737 (Oct. 17, 1989), Wilson et al, U.S. Pat. No.4,971,936 (Nov. 20, 1990), and Job et al, U.S. Pat. No. 5,229,477 (Jul.20, 1993), which are all herein incorporated by reference.

[0043] A preferred catalyst for use herein is described in Job U.S. Pat.No. 5,122,494 (Jun. 19, 1992). The catalyst is formed by contacting, inthe presence of an inert diluent, an alkyl aluminum halide halogenatingagent with a complex magnesium-containing, titanium-containing alkoxidecompound prepared by reaction of magnesium alkoxide, titaniumtetra-alkoxide and a phenolic compound. The complex alkoxide compoundsare of somewhat variable stoichiometry but have the general illustrativeformula

Mg₃Ti(OR′″)₈X₂

[0044] wherein R′″ independently is alkyl of up to four carbon atomsinclusive and X independently is a monovalent anion derived from anelectron donor such as a phenolic compound, aldehyde or ether asdescribed herein. The diluent is then removed to produce, as aparticulate solid, the complex alkoxide compound. This solid is treatedwith alkyl aluminum halide to produce the olefin polymerizationcatalyst.

[0045] The preferred alkoxides are magnesium ethoxide, Mg(OEt)₂, andtitanium-tetraethoxide. The phenolic compound is selected from phenol oran activated phenol (a monohydroxylic phenol of one aromatic ring havingaromatic ring substituents other than hydrogen which serve to alter thepKa of the phenolic compound). Suitable phenolic compounds are phenol,o-cresol, and 2,6-di-t-buty-4-methylphenol (BHT). An election donor asdescribed hereinabove or hereinbelow can also be used.

[0046] The α-olefin backbone monomer and the comonomer may becationically polymerized by reacting them in the presence of a cationicpolymerization initiator in the presence of a Lewis acid and, generally,an electron donor. The Lewis acid and the electron donor may becomplexed together. Lewis acids which can be utilized herein includemetal halides, such as aluminum trichloride (and molten salts containingaluminum trichloride), boron trichloride, boron trifluoride and titaniumtetrachloride, and organometallic derivatives, such asethylaluminumdichloride and triethyl aluminum, and oxyhalides, such asphosphorus oxychloride. Electron donors which are useful herein includealkyl amines, pyridines, such as 2,6-lutidiene and 2,4,6-collidine,triaryl or trialkyl phosphines, benzaldehyde, ethers such as1,2-dioxybenzene and veratrole. The cationic polymerization initiatorsare generally taken from the group consisting of tertiary alkyl halidessuch as t-butylchloride and triphenymethylfluoride.

[0047] The preferred Lewis acids are aluminum trichloride and borontrichloride because of their higher activity. The preferred electrondonors are 2,6-lutidine and benzaldehyde because they have been shown togive random copolymers and highly amorphous polymers, respectively (Jobet al, U.S. Pat. No. 5,134,209 (Jul. 28, 1992) and the Job U.S. Pat. No.5,229,477 patent. The preferred cationic polymerization initiators arecumyl-type derivatives like cumylchloride, alkoxide, or aliphatictertiary chlorides.

[0048] The cationic polymerization may be a batch, semi-continuous, or acontinuous process. Generally, the polymerization is carried out at atemperature of from about −100 to about 0° C. under a pressure of from 0to 10 atm. Another method for copolymerizing the α-olefins and thefunctionalized monomers is free radical polymerization.

[0049] In the second embodiment of the invention, the backbone is simplya conventional ethylene/propylene diene monomer (EPDM) polymer which ismetallated in a manner known in the art so as to provide sites for theanionic polymerization of a monovinylarene anionically polymerizablemonomer “from” the backbone. The production of the EPDM polymers and thelithiation thereof are known in the art as shown in Lund et al, U.S.Pat. No. 4,786,689 (Nov. 22, 1988); and Lund et al, U.S. Pat. No.4,794,145 (Dec. 27, 1988), the disclosures of which are herebyincorporated by reference. These reactions generally involve themetallation of allylic sites in the olefinic moieties of the dienemonomer by reaction with alkyllithium compounds in the presence ofactivators. These lithiated sites then serve as initiator sites toinitiate the polymerization of subsequently added anionicallypolymerizable monomer.

[0050] Side Chain Formation—First Embodiment

[0051] In the first aspect of the first embodiment of this invention, aliving aromatic polymer side chain is produced by anionic polymerizationas described hereinabove with regard to the preparation of the olefinterminated polystyrene comonomer in the third aspect of the firstembodiment of this invention. The only difference being that instead ofterminating the living polymer with a alkenyl halosilane to give amacromer, the living polymer chain is left intact and reacted with thefunctional group supplied by the comonomer. This results in grafting theliving aromatic polymer chain to the amorphous backbone at the site ofthe comonomer incorporation.

[0052] By living polymer chains it is meant that the polymerizationinitiator is still a part of the polymer chain and is active andavailable for further polymerization if more monomer becomes available.In this case, the polymerization is ended when the monomer supply isexhausted. For example, when polystyrene is polymerized and an organolithium compound is used as the initiator, the living polymer chain canbe represented as

PS⁻Li⁺

[0053] This is known as polystyryl lithium.

[0054] A particularly desireable feature of this embodiment of thepresent invention is the ability to produce a saturated graft blockcopolymer without the necessity for a hydrogenation step. By“saturation” is meant no or essentially no aliphatic unsaturation.Saturated graft block copolymers are produced in the first aspect ofthis embodiment since the anionically polymerized monomer is one whichcontains a single aliphatic double bond. Examples are vinyl aromatichydrocarbons, particularly styrene, substituted styrenes, and ethylene.When these monomers are utilized the result is a saturated graft blockcopolymer.

[0055] The final step of the first aspect of this embodiment isaccomplished as noted above by grafting the living polymer chains ontothe copolymer. For halosilane comonomers, this takes place byreplacement of a halogen attached to the silicon with the living polymerchain. This is accomplished by reacting the two polymers in the presenceof an activator such as tetramethylethylenediamine or ethers such asglyme (1,2-dimethoxyethane), o-dimethoxybenzene, or ethylene glycoldiethylether, at a temperature of 30 to 100° C. and a pressure of 1 to10 atm. This step also can be carried out in the absence of activatorsbut it proceeds more slowly to completion.

[0056] The copolymerization of the α-olefin and the 1-alkenylfunctionalized comonomer produces a polymer with a saturated olefinicbackbone having pendent saturated alkyl chains having a functional groupattached thereto which may be a terminal group or which may be in theinternal portion of the chain. Such copolymers may be represented by thefollowing:

[0057] The living polymer chains react with these copolymers at thesilicon trichloride sites and the polymer chain takes the place of achloride on the silicon trichloride group in the polymer so that itbecomes part of a pendent side chain. In the case of a polystyryllithium living polymer, the above copolymer is converted to a saturatedgraft block copolymner with the following formula:

[0058] In the second aspect of the first embodiment of the invention,the backbone is metallated (“lithiated” when lithium is the metal) byreaction with a metal alkyl or aryl compound, especially alkyl lithium(RLi) compounds such as sec-butyl lithium or n-butyllithium in thepresence of a polar metallation activator. The RLi compound lithiates(metallates) one of the carbons, generally by abstraction of thebenzylic hydrogen. Thus, in the context of this invention the benzylicposition constitutes a functional group as noted previously. Thisresults in the following structure when n is 0:

[0059] When n is 1 to 20 it results in the following structure:

[0060] Some metallation of the benzene ring itself can also occur. Inany event, the resulting

[0061] then serves as a subsequent initiation site for anionicallypolymerizable monomers to polymerize out “from” the backbone to producependant side chains.

[0062] An activator is generally required to catalyze the metallationreaction. Suitable activators include tertiary aliphatic amines,tertiary diamines, and triamines. Preferred activators includedipiperidinoethane and tetramethyl-ethylene-diamine (TMEDA). Themetallation reaction is generally carried out at 0 to 100° C.,preferably 25 to 60° C. for a time within the range of 1 minute to 24hours, preferably 30 minutes to 1 hour. Suitable solvents for themetallation include saturated non-aromatic solvents such as cyclohexane.Generally, the comonomer is employed in an amount just sufficient togive about the number of sites desired for pendant chains. Accordingly,the metallation promoter is generally present in an amount of about 1equivalent per polymerized comonomer unit. However, this could besubject to wide variation. For instance, more sites could beincorporated into the backbone than necessary and hence less than astoichiometric amount of metallation agent would be used. Alternatively,an excess may be used so as to speed up the metallation with excessthereafter being removed. More detail concerning the metallation can befound in Gergen and Lutz, U.S. Pat. No. 4,898,914 (Feb. 6, 1990), thedisclosure of which is hereby incorporated by reference. All of theconditions broadly set out in the above-described patent are applicableherein.

[0063] Once the metallation reaction is complete, there will be a numberof metallated sites on the copolymer which are available for growth ofanionically polymerized polymer side chains.

[0064] The final step of the process of preparing the polymer to befunctionalized in this second aspect of the first embodiment of thisinvention is accomplished, for example, by growing the living polymerchains from the lithiated α-olefin/vinyl aromatic copolymer byinitiation and subsequent polymerization from the lithiated sites withthe anionically polymerizable monomer. This is accomplished by reactingthe backbone metallated copolymer and the anionically polymerizablemonomer in a suitable solvent. Generally, reaction temperature rangesfrom about −150° C. to about 300° C., preferably 0° C. to 100° C.Reaction time generally ranges from about 5 minutes to about 24 hours,preferably 30 minutes to 3 hours. Reaction pressure is generally 1-10atmospheres.

[0065] As noted hereinabove, the polymer to be functionalized is alreadycomplete in the third embodiment of the first aspect of this inventionsince the comonomer itself is a macromer which carries the pendantaromatic site chain.

[0066] Side Chain Formation—Second Embodiment

[0067] In the second embodiment of this invention, the EPDM backbonepolymer is metallated as is known in the art and then a monoalkenylaromatic monomer grafted “from” the metallated site as in the secondaspect of the first embodiment of the invention. This embodiment of theinvention is less preferred because from about 1 to 4% unsaturationremains in the rubber backbone due to diene comonomer and these sitesare prone to degradation in the presence of heat and/or chemicalsresulting in the loss of material properties.

[0068] Functionalization

[0069] The amorphous backbone polymers of this invention can befunctionalized in the same manner as conventionally preparedthermoplastic elastomers. Such techniques are disclosed, for instance,in Gergen et al, U.S. Pat. No. 4,578,429 (Mar. 25, 1986), the disclosureof which is hereby incorporated by reference. Briefly, this can bedescribed as follows.

[0070] In order to incorporate functionalities into the base polymer,monomers capable of reacting with the base polymer, for example, insolution or in the melt, by free radical mechanism are necessary.Monomers may be polymerizable or nonpolymerizable, however, preferredmonomers are non-polymerizable or slovenly polymerizing.

[0071] The monomers must be ethylenically unsaturated in order to takepart in free radical reactions. It has been found that by graftingunsaturated monomers which have a slow polymerization rate, theresulting graft copolymers contain little or no homopolymer of theunsaturated monomer and contain only short grafted monomer chains whichdo not separate into separate domains.

[0072] The class of preferred functionalizing monomers which will formpolymers within the scope of the present invention have one or morefunctionalities or their derivatives such as carboxylic acid groups andtheir salts, anhydrides, esters, imide groups, amide groups, acidchlorides and the like in addition to at least one point ofunsaturation.

[0073] These functionalities can be subsequently reacted with othermodifying materials to produce new functional groups. For example agraft of an acid-containing monomer could be suitably modified byesterifying the resulting acid groups in the graft with appropriatereaction with hydroxy-containing compounds of varying carbon atomlengths. The reaction can take place simultaneously with the grafting orin a subsequent post modification reaction.

[0074] The functionalized polymer will usually contain from 0.02 to 20,preferably 0.1 to 10, and most preferably 0.2 to 5 weight percent offunctionality.

[0075] The preferred functionalizing monomers are unsaturated mono- andpolycarboxylic-containing acids (C₃-C₁₀) with preferably at least oneolefinic unsaturation, and anhydrides, salts, esters, ethers, amides,nitriles, thiols, thioacids, glycidyl, cyano, hydroxy, glycol, and othersubstituted derivatives from said acids.

[0076] Examples of such acids, anhydrides and derivatives thereofinclude maleic acid, fumaric acid, itaconic acid, citraconic acid,acrylic acid, glycidyl acrylate, cyanoacrylates, hydroxy C₁-C₂₀ alkylmethacrylates, acrylic polyethers, acrylic anhydride, methacrylic acid,crotonic acid, isocrotonic acid, mesacronic acid, angelic acid, maleicanhydride, itaconic anhydride, citraconic anhydride, acrylonitrile,methacrylonitrile, sodium acrylate, calcium acrylate, and magnesiumacrylate.

[0077] Other functionalizing monomers which can be used either bythemselves or in combination with one or more of the carboxylic acids orderivatives thereof include C₂-C₅₀ vinyl monomers such as acrylamide,acrylonitrile and monovinyl aromatic compounds, i.e. styrene,chlorostyrenes, bromostyrenes, α-methylstyrene, and vinyl pyridines.

[0078] Other functionalizing monomers which can be used are C₄ to C₅₀vinyl esters, vinyl ethers and allyl esters, such as vinyl butyrate,vinyl laurate, vinyl stearate, and vinyl adipate, and monomers havingtwo or more vinyl groups, such as divinyl benzene, ethylenedimethacrylate, triallyl phosphite, dialkylcyanurate and triallylcyanurate.

[0079] The preferred functionalizing monomers to be reacted with theblock copolymers according to the present invention are maleicanhydride, maleic acid, fumaric acid and their derivatives. It is wellknown in the art that these monomers do not polymerize easily.

[0080] Of course, mixtures of functionalizing monomers can be also addedso as to achieve functionalized copolymers in which the copolymercontains at least two different functionalizing monomers therein.

[0081] Reaction temperatures and pressures should be sufficient to meltthe reactants and also sufficient to thermally decompose the freeradical initiator to form the free radical. Reaction temperatures woulddepend on the base polymer being used and the free radical initiatorbeing used. Typical reaction conditions can be obtained by using a screwtype extruder to mix and melt the reactants and to heat the reactantmixture to the desired reaction temperature.

[0082] The temperatures useful in the reaction of the process of thepresent invention may vary between wide limits such as from +75° C. to450° C., preferably from about 200° C. to about 300° C.

[0083] It is to be noted that since the side chain-containing backboneis already formed before this functionalization, the functional groupsare attached directly to the block copolymer as opposed to already beingon the chain and serving as a site for the side chains.

[0084] Definitions

[0085] As used herein “functionalized,” “functionalizing” and“functionality” refer to the final treatment with the componentcontaining at least one point of saturation such as maleic anhydride.“Functional group” and “functional to” refer to characteristics of thecomonomer used in the second aspect of the first embodiment of thisinvention.

[0086] Utility

[0087] The block copolymers, as modified, can still be used for anypurpose for which an unmodified material (base polymer) was formerlyused. That is, they can be used for adhesives and sealants, orcompounded and extruded and molded in any convenient manner.

EXAMPLE

[0088] Melt Phase Functionalization of Poly(α-olefin)-g-PolystyrenePolymers with Maleic Anhydride

[0089] Maleic anhydride functionalization of two α-olefin backbonethermoplastic elastomers and one EPDM backbone thermoplastic elastomerwas studied. A conventional thermoplastic elastomer prepared forcomparison with the invention by sequentially polymerizing styrene,butadiene and then styrene followed by termination of the polymerchains, hydrogenation and hydrogenation catalyst removal was used as acomparison polymer. This polymer was used since such polymers are knownto efficiently graft maleic anhydride in the melt in the presence of anorganic peroxide. Characteristics of the polymers used are given inTable 1. Maleic Anhydride powder was dry blended with the polymer crumb,and 0.2 wt % 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (sold under thetradename Lupersol 101 by Lucidol Pennwalt) was dispersed into themixture as a 0.5 wt % solution in acetone. The mixtures were blended ina Custom Scientific Instruments melt mixer with a 5 cm³ capacity at200-210° C. and 70-80 rpm for one minute. The products were thenanalyzed by FTIR to determine the weight % maleic anhydride grafted tothe polymers. In addition, films were cast from toluene andstress/strain properties measured for comparison with the polymersbefore functionalizing.

[0090] Results of free radical functionalizing grafting are given inTable 2.

[0091] Sample KT-24H was prepared in accordance with the firstembodiment, first aspect of this invention. Specifically, 1-hexene and 2mole % allyl dimethyl-chlorosilane were copolymerized using aMg₆(OCH₂CH₃)₁₀TiCl₄(benzaldehyde)₂ catalyst with an ethyl aluminumdichloride cocatalyst to give an amorphous copolymer. Styrene waspolymerized using a sec butyl lithium initiator and the resulting livingpolystyrene chains reacted with the copolymer to give saturatedthermoplastic elastomer.

[0092] AZN-4A was prepared in accordance with the first embodiment,second aspect. Specifically, octene and 4-phenyl-1-butene werecopolymerized using a Mg₆(OXCH₂CH₃)₁₀TiCl₄(benzaldehyde)₂ catalyst witha triethylaluminum co-catalyst to give an amorphous polymer. Theresulting polymer was metallated with secondary butyllithium usingN,N,N′,N′-tetramethyl ethylenediamine as a promoter. Separately, styrenewas introduced and a styrene polymer chain formed by anionicpolymerization from the metallation site which acted in the manner of aconventional initiator.

[0093] ZNA-2G contains a backbone of a commercial EDPM sold under thetradename Nordell 1320 by DuPont. This material was then maleated andstyrene grown from the metallation site as in AZN-4A above.

[0094] The composition labeled “comparison” was prepared as describedhereinabove. TABLE 1 Polymer Characteristics Number of PolystyrenePolystyrene Grafts/ Content MW 100K backbone Polymer Structure (%)^(c)(g/mole)^(f) Mw^(i) KT-24H C₆-g-PS^(a) 31 6000^(g) 7.5 AZN-4AC₈-g-PS^(b) 22 6000^(g) 4.7 ZNA-2G EPDM-g-PS^(c) 43 9000^(g) 8.4Comparison S-EB-S^(d) 30 7200/7700^(h) —^(a)Poly(1-hexane)-g-polystyrene ^(b)Poly(1-octene)-g-polystyrene^(c)EPDM-g-polystyrene ^(d)Styrene-Hydrogenated Butadiene-Styrenetriblock copolymer ^(e)Determined by ¹H NMR ^(f)Determined by GPC^(g)Values reported are for each polystyrene graft ^(h)Values reportedare for first and second polystyrene block${\quad^{i}{Calculated}\quad {using}\quad {the}\quad {following}\quad {equation}\text{:}\quad {Ng}} = \frac{100\text{,}000 \times {wg}}{{Mg} \times ( {1 - {wg}} )}$

where Ng = number of grafts per 100,000 g/mole of backbone wg = weightfraction of graft (PS) in the graft copolymer Mg = number averagemolecular weight of the graft (PS) in the graft copolymer

[0095] TABLE 2 Tensile Properties^(c) Tensile Properties^(c) BeforeMaleic After Maleic Anhydride Grafting Anhydride Grafting MA MA GraftUltimate Ultimate Ultimate Ultimate Added grafted^(a) Efficiency^(b)Strength Elongation Strength Elongation Sample (wt %) (wt %) (%) (psi)(%) (psi) (%) KT-24H 2.3 0.3 9.6 342 ± 35  239 ± 101 205 ± 46  126 ± 55AZN-4A 2.3 0.32 14 830 ± 58  1166 ± 77  323 ± 4  204 ± 4  ZNA-2G 2.30.57 25 2574 ± 582  909 ± 66  1379 ± 106  428 ± 18 Comparison 3.1 0.9742 6439 ± 231  681 ± 20  3097 ± 403  725 ± 29 ^(a)Deternined by FTIRusing an experimentally determined correlation betweeb polystreneabsorbance and carbonyl absorbance ^(b)Calculated as follows:${\% \quad {Graft}\quad {efficiency}} = {( \frac{\% \quad w\quad {MA}\quad {Grafted}}{\% \quad w\quad {MA}\quad {Added}} ) \times 100}$

^(c)Test performed on an INSTRON ® Model 4505 with a gauge length of 1inch and a cross head speed of 1 inch/min. Values reported are the mean± s.d. of at least three independent measurements on compression moldedfilms.

[0096] As can be seen, the expected Beta-scission did not reduce thematerial to a useless condition. Perhaps less Beta-scission occurredthan would have been predicted or perhaps this surprising resultreflects the fact that there are more polystyrene blocks per polymerchain than in a conventional triblock copolymer and thus a significantfraction of the polymer backbones still contain at least two grafts toform a mechanical network. Furthermore, when conventional thermoplasticelastomers are hydrogenated and functionalized, some aliphaticunsaturation generally remains and some of the aromatic unsaturation isdestroyed. Here, the saturated elastomers have no or essentially noaliphatic unsaturation and all of the original aromatic unsaturationremains.

[0097] While this invention has been described in detail for the purposeof illustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

1. A process for producing a functionalized saturated thermoplasticelastomer which comprises: (a) copolymerizing: (i) a monomer systemselected from the group consisting of at least one C₄-C₃₀ α-olefins andethylene plus 20 to 40 mole % of a higher α-olefin with (ii) a 1-alkenylcomonomer containing a functional group to which a polymer chain formedby anionic polymerization can be grafted to produce a graft blockcopolymer; (b) anionically polymerizing at least one monoalkenylaromatic compound to form living polymer chains; (c) grafting saidliving polymer chains onto said block copolymer to form saidthermoplastic elastomer, said elastomer having a saturated olefinicbackbone with pendant polyarene side chains; and (d) contacting saidthermoplastic elastomer with a free radical initiator and afunctionalizing monomer having at least one point of unsaturation.
 2. Amethod according to claim 1 wherein said functionalizing monomer isselected from carboxylic acids and derivatives of carboxylic acids.
 3. Amethod according to claim 2 wherein said monomer system is ethylene and20-40 mole % propylene.
 4. A method according to claim 2 wherein saidmonomer system is a single monomer selected from hexene and octene.
 5. Amethod according to claim 2 wherein said comonomer is a1-alkenylhalosilane.
 6. A method according to claim 2 wherein said freeradical initiator is a peroxide.
 7. A method according to claim 2wherein said copolymerization takes place in the presence of a catalystcomprising Mg(OCH₂CH₃)₁₀TiCl₄(benzaldehyde)₂ with an ethyl aluminumdichloride cocatalyst and an electron donor selected from benzaldehydeand 1,2-diethoxybenzene.
 8. A method according to claim 1 wherein saidmonomer system is selected from hexene and octene, said comonomer isallyldimethylchlorosilane, said living polymer chains are formed fromstyrene initiated with secondary butyllithium, said free radicalinitiator is 2,5-dimethyl-2,5-di-(t-butylperoxy)-hexane and saidfunctionalizing monomer is maleic anhydride and said maleic anhydride isincorporated in an amount within the range of 0.2 to 5 weight percent.9. A product produced by the method of claim
 8. 10. A product producedby the method of claim
 1. 11. A process for producing a functionalizedsaturated thermoplastic elastomer which comprises: (a) copolymerizing:(i) a monomer system selected from at least one C₄-C₃₀ α-olefin andethylene plus 20 to 40 mole percent of a higher α-olefin with (ii) acomonomer selected from

and CH₂═H—(CH₂)_(n)—SiR_(m)H_(x) wherein R is selected from alkyl andaryl, x is 0-1, m is 2-3 and x+n=3, said comonomer containing afunctional group from which an anionically polymerized polymer is grownto produce a graft block copolymer; (b) metallating said functionalgroup on said comonomer by reaction with an organo-alkali metal compoundin the presence of a metallation activator; (c) reacting the thusmetallated copolymer with at least one monoalkenyl aromatic compound toform a thermoplastic elastomer having a saturated olefinic backbone withpendant anionically polymerized monoalkenyl aromatic compound sidechains; and (d) contacting said thermoplastic elastomer with a freeradical initiator and a functionalizing monomer having at least onepoint of unsaturation.
 12. A process according to claim 11 wherein saidcopolymerizing is done using a catalyst formed fromMg₆(OCH₂CH₃)₁₀TiCl₄(benzaldehyde)₂ with a triethylaluminum cocatalystand treated with a composition selected from the group consisting ofbenzaldehyde and 1,2-diethoxybenzene.
 13. A method according to claim 11wherein said comonomer is allyltrimethyl silane.
 14. A method accordingto claim 11 wherein said monomer system is a single monomer selectedfrom hexene and octene, said comonomer is selected from allylbenzene and4-phenyl-1-butene, said metallating is done with sec-butyllithium, saidmetallation activator is N,N,N′,N′-tetramethylethylenediamine, saidmonoalkenyl aromatic compound is styrene, said free radical initiator isa peroxide and said functionalizing monomer is maleic anhydride saidmaleic anhydride being incorporated in an amount within the range of 0.2to 5 weight percent.
 15. A product produced by the method of claim 14.16. A product produced by the method of claim
 11. 17. A process forproducing a functionalized saturated thermoplastic elastomer comprising:(a) copolymerizing, under polymerization conditions to form athermoplastic elastomer (i) a monomer system selected from (a) at leastone C₄ to C₃₀ α-olefin and (b) ethylene with 20 to 40 mole percent of ahigher α-olefin, and (ii) a comonomer of the general formula

wherein R′ is the remnant of an initiator, R″ is a polymerizedmonoalkenyl arene unit, R is alkyl, n is an integer of from 0 to 16, andx is an integer sufficient to give said monomer a molecular weightwithin the range of 500-30,000; and (b) contacting said thermoplasticelastomer with a free radical initiator and a functionalizing monomerhaving at least one point of unsaturation.
 18. A method according toclaim 17 wherein said functionalizing monomer is selected fromcarboxylic acids and derivatives of carboxylic acids.
 19. A methodaccording to claim 17 wherein R′ is is the remnant of an unsaturatedinitiator, said comonomer thus being an α,ω-olefin.
 20. A methodaccording to claim 17 wherein (a) said comonomer is formed by reactingan alkyl alkali metal initiator with a monoalkenyl aromatic compound togive a living aromatic polymer chain said reacting being done in anα-olefin solvent selected from C₆ to C₃₀ olefins; (b) thereafterreacting said living aromatic polymer chain with an alkenyl halosilanein the presence of a solvent which is an α-olefin selected from C₄ toC₃₀ α-olefin; and (c) thereafter reacting said comonomer with a monomerwhich is an α-olefin selected from C₄ to C₃₀ α-olefins to give asaturated thermoplastic elastomer, no other solvent being used in saidmethod.
 21. A method according to claim 20 wherein said α-olefin of (A),(B), and (C) is the same α-olefin.
 22. A method according to claim 17wherein said monomer system is a single monomer selected from octene anddecene, said comonomer is the reaction product of a living polystyrenelithium chain and 6-hex-1-enyl dimethylchlorsilane, said copolymerizingis done in the presence of a transition metal catalyst.
 23. Acomposition produced by the method of claim
 22. 24. A compositionproduced by the method of claim
 17. 25. A process for producing afunctionalized saturated thermoplastic elastomer which comprises: (a)copolymerizing: (i) a monomer system selected from at least one C₄ toC₃₀ α-olefin and ethylene plus 20 to 40 mole percent of a higherα-olefin with (ii) a comonomer formed by terminating a livingpolystyrene-lithium chain having a vinyl group at an end of said chainopposite the thus terminated lithium to produce a thermoplasticelastomer; and (b) contacting said thermoplastic elastomer with afunctionalizing monomer having at least one point of unsaturation.
 26. Aprocess comprising: metallating an EPDM polymer; contacting the thusmetallated EPDM polymer with at least one monoalkenyl aromatic compoundunder anionic polymerization conditions to form anionically polymerizedmonoalkenyl aromatic compound side chains, thus giving a thermoplasticelastomer; and contacting said thermoplastic elastomer with a freeradical initiator and a functionalizing monomer having at least onepoint of unsaturation.
 27. A method according to claim 26 wherein saidmetallating is done with secondary butyllithium, said monoalkenylaromatic compound is styrene, said free radical initiator is a peroxideand said functionalizing monomer is a maleic anhydride.
 28. A productproduced by the method of claim
 27. 29. A product produced by the methodof claim 26.